Printer cartridge and memory device containing a compressed color table

ABSTRACT

A printer cartridge includes a memory device and at least one compressed color table stored on the memory device. A compressed color table includes a losslessly compressed neutral axis, a number of nodes that correspond to seed color table nodes and a number of delta nodes that correspond to a number of delta tables. The number of delta tables indicate differences between interpolated color table nodes and corresponding actual color table nodes.

BACKGROUND

Many output devices such as ink printers and laser printers implement asubtractive color model while input devices such as computer monitors,mobile phones, and other input devices implement an additive colormodel. For example, output devices may use a CMYK (cyan, magenta, yellowand black) color model, while input devices may use a RGB (red, greenand blue) color model. To output data from an input device such as agraphic, text or a combination thereof, output devices convert theadditive color model into a subtractive color model.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various examples of the principlesdescribed herein and are a part of the specification. The illustratedexamples do not limit the scope of the claims.

FIG. 1 is a diagram of input devices, an output device, and a printercartridge, according to one example of the principles described herein.

FIG. 2 is a diagram of a memory device containing a compressed colortable, according to one example of the principles described herein.

FIG. 3 is a diagram of a compressed color table, according to oneexample of the principles described herein.

FIG. 4 is a diagram of a compressed color table, according to oneexample of the principles described herein.

FIG. 5 is another diagram of a compressed color table, according to oneexample of the principles described herein.

FIG. 6 is another diagram of a compressed color table, according to oneexample of the principles described herein.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION

Input devices may implement an additive color model to visually displaytext or images. For example, an input device may implement a RGB colormodel. An input device may implement various types of RGB color models.Examples of RGB color models include sRGB, Adobe® RGB and scan RGB. Asused herein, the various types of RGB color models may be referred togenerically as a RGB color model, or similar terminology.

Before an input image can be printed as a physical output, the inputadditive color model (RGB, for example) is converted to an outputsubtractive color model (CMYK, for example). This may be done using acolor transformation table that converts RGB color data into CMYK colordata.

However, current color transformation processes may produceunsatisfactory results. For example, often, the content of the colortransformation from an additive model to a subtractive model is highlydependent on the output media formulation. For example, the colortransformation may be dependent on fluid properties of the ink, theink's reflective properties when printed on various substrates, andother inherent properties of the ink or toner. As a result, differentcartridges, and different ink types may output different representationsof input color. Additionally, the output device may rely on a number ofcolor transform tables which can be large and take up valuable memoryspace.

Thus, the present disclosure describes a memory device, for example foruse with, or disposed on a printer cartridge. The memory device containsa number of compressed color tables. While the attached description mayrefer to a single compressed color table, the memory device may containa number of compressed color tables. A compressed color table comprisesa losslessly compressed neutral axis. A number of nodes of thecompressed color table correspond to a number of seed color table nodes.The compressed color table also comprises a number of delta nodes thatcorrespond to delta values from a number of delta tables. The deltatables may indicate differences between interpolated color table nodesand corresponding actual color table nodes.

As described herein, the compressed color table stored on the memorydevice may allow for perceptually lossless compression of color tablesat significant compression rates. Accordingly, the compressed colortable may allow for lossy to lossless compression results while meetingthe storage allocation of a memory device of a printer cartridge. In oneexample, the compressed color table preserves the neutral axis of thecolor table, which corresponds to those colors that are most susceptibleto error perception by the human eye, thus increasing the overallquality of the compressed color table.

In one example, a memory device, that may be disposed on a printercartridge, can be beneficial in that the color tables need not bedisposed on a printer or other electronic device. The color table isoptimized for the inks in the cartridge. For example, updates andadjustments to the color tables would not require pushing table updatesvia a printer program instruction or a printer driver update.Additionally, a memory device that comprises the compressed color table,affords greater flexibility and customization in the selection and useof various printer cartridges.

In the present specification and in the appended claims, the term“lossless compression,” or similar language, may include compressionwherein the original data, may be reconstructed from the compresseddata, such that the differences between the original data and thecompressed data are imperceptible. More specifically, “digitallylossless compression” may include compression where there will be nodigital difference between the original data and the compressed data and“perceptually lossless compression” may include compression where theremay be digital differences between the original data and the compresseddata, but the differences may not be visible to the consumer of thedata. The neutral axis and the seed color table may be digitallylosslessly compressed. Additionally, in the present specification, theterm “lossy compression,” or similar language, may include compressionwherein a portion of the original data is discarded during compression.As will be described below, the delta tables may be digitally lossless,perceptually lossless, or lossy.

Yet further, in the present specification and in the appended claims,the terms “seed color table,” “intermediate color table,” and “finalcolor table” may include an initial, intermediate and final, orend-result, color table, respectively. In some examples, the seed colortable may be a lower resolution color table, the intermediate colortable may be a middle resolution color table, and the final color tablemay be a higher resolution color table. It should be noted that thefinal color table is different than the compressed color table. Forexample, the final color table is a high resolution color table that maynot be compressed. By comparison, the compressed color table may be ahigh resolution color table that is compressed.

Yet further still, in the present specification and in the appendedclaims, the term “interpolated color table” or similar terminology mayinclude a color table that comprises 1) a number of actual nodes thatcorrespond to nodes from a lower resolution color table and 2) a numberof interpolated nodes that are interpolated from the lower resolutioncolor table using any mathematical interpolation method. Theinterpolated nodes may include interpolated node values.

By comparison, in the present specification, the term “seed/delta colortable” or similar terminology may include a color table thatcomprises 1) a number of actual nodes that correspond to nodes from alower resolution color table, 2) a number of delta nodes that are basedon values from a delta table, the delta table reflecting differencesbetween an actual color table and an interpolated version of the colortable. From these differences node values may be reconstructed from thedelta nodes during decompression.

Still further, in the present specification and in the appended claims,the term “neutral axis” may include a line extending from the origin ofa three-dimensional color table to the node of the color table farthestfrom the origin. One of the origin node and the farthest nodecorresponds to the color white, and the other corresponds to the colorblack. Colors along the neutral axis may be referred to as “neutralcolors,” “near-neutral colors,” or similar terminology and may be thosecolors where small differences or errors are most accurately discernedby the human eye. Accordingly, deviations along the neutral axis aremore easily perceived by the human eye.

Lastly, as used in the present specification and in the appended claims,the term “a number of” or similar language may include any positivenumber comprising 1 to infinity; zero not being a number, but theabsence of a number.

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present systems and methods. It will be apparent,however, to one skilled in the art that the present apparatus, systems,and methods may be practiced without these specific details. Referencein the specification to “an example” or similar language means that aparticular feature, structure, or characteristic described is includedin at least that one example, but not necessarily in other examples.

FIG. 1 is a diagram of input devices (101), an output device (102), anda printer cartridge (103), according to one example of the principlesdescribed herein. In some examples, via an input device (101) a user maygenerate data to be output in tangible form. The data may be text, animage, or combinations thereof. In one example of generating input to bephysically output, a user may use a word processing computer program ona computer or laptop to generate a text document. In another example, auser may generate, or otherwise obtain a graphic. Examples of inputdevices (101) include, computers, laptops, digital cameras, mobiledevices, personal digital assistants (PDAs), tablets, and other inputdevices. An output device (102) may be used to output a physical versionof the generated data. For example, a printer may print the textdocument or the graphic onto paper. Examples of output devices (102)include, but are not limited to, laser printers and ink printers.

A printer cartridge (103) may be used with an output device (102) togenerate a physical output based on information received from an inputdevice (101). For example, the printer cartridge (103) may be an inkcartridge that contains liquid ink for use with an inkjet printer. Inanother example, the printer cartridge (103) may be a toner cartridgethat contains dry toner powder for use with a laser printer. As will bedescribed below, the printer cartridge (103) may comprise a number ofcompressed color tables that convert an input device (101) color modelto an output device (102) color model.

In some examples, a number of printer cartridges (103) may be used withan output device (102) to generate an output. For example, when usedwith an inkjet printer, multiple printer cartridges (103) may be used.More specifically, one printer cartridge (103) may include black ink andanother printer cartridge (103) may include cyan, magenta and yellowink. In another example, one printer cartridge (103) may include blackink, another printer cartridge (103) may include cyan ink, anotherprinter cartridge (103) may include magenta ink, and another printercartridge (103) may include yellow ink. Accordingly, each printercartridge (103) may contain a number of compressed color tablescorresponding to the ink colors included in the printer cartridge (103).While FIG. 1 depicts a number of input devices (101), and an outputdevice (102), the present specification is directed to a printercartridge (103). Specifically, the present specification is directed toa printer cartridge (103) and memory device containing a compressedcolor table.

FIG. 2 is a diagram of a memory device (204) containing a compressedcolor table (205), according to one example of the principles describedherein. The memory device (204) may store data relating to theconversion of input data to output data. For example, the memory device(204) may store a number of compressed color tables (205) that convertan input color model into an output color model. The memory device (204)may be implemented with other electronic components to generate aphysical output. For example, the memory device (204) may be coupled toa printer cartridge controller (not shown) that controls thedistribution of an output media (e.g., ink or toner) onto a physicalsubstrate. In some examples, a memory device (204) may be disposed onthe printer cartridge (103). In other examples, the memory device (204)may be independent of the printer cartridge (103) and programmed to beused with the printer cartridge (103).

As described above, the memory device (204) may store a number ofcompressed color tables (205) that transform received data from an inputcolor model to an output color model. More specifically, a compressedcolor table (205) may specify the transformations of an input RGB model(such as sRGB, adobe RGB, scan RGB, for example) to an output CMYKmodel. While the present specification discusses the colortransformation with regards to a three-dimensional RGB color model, thecompressed color tables (205) may convert any number, and any type, ofinput color models into any number, and any type, of output colormodels. Examples of color models that may be converted include, but arenot limited to, the Specifications for Web Offset Publications (SWOP)CMYK model, and the International Commission on Illumination (CIE)L*a*b* color model.

As will be described in more detail in connection with FIG. 3, thecompressed color table (205) may be represented by a three-dimensionalcube having a number of nodes. The nodes may indicate output colorantamounts. In this representation, the compressed color table (205) mayinclude a losslessly compressed neutral axis, a number of nodescorresponding to nodes of a seed color table and a number of delta nodesthat correspond to a number of delta tables, the delta tables indicatingdifferences between corresponding nodes on an interpolated color tableand an actual color table.

Storing the compressed color table (205) on a memory device (204) eitherused with, or disposed on, a printer cartridge (103) may be beneficialin that it allows greater flexibility in output media customization. Forexample, updates to the color transformation may be distributed via theprinter cartridges (103) as opposed to pushing printer programinstructions or printer driver updates. Additionally, as the colortransformation is heavily dependent on the ink or toner formulation, amore accurate representation of the input color model may be generatedwhen the compressed color table (205) is stored on, and tailored to, aspecific printer cartridge (103) rather than stored on an output device(FIG. 1, 102) that may implement various kinds of printer cartridges(103). Additionally, compressed color tables (205) may be updated as inkor toner formulation changes.

FIG. 3 is a diagram of a compressed color table (205), according to oneexample of the principles described herein. As described above, in someexamples, the compressed color table (205) may be represented as athree-dimensional cube. Each axis of the cube may correspond to a colorof the input color model. For example, the x-axis (306) may correspondto the color green, the y-axis (307) may correspond to the color red,and the z-axis (308) may correspond to the color blue. A number of linesmay divide each plane of the cube as indicated in FIG. 2 by the dashedlines. For simplicity, in FIG. 3, just a single line has been indicatedby a reference numeral. The intersection of two lines is designated as anode (309) that indicates a transformation from the input colorantindicated by the index of the node (309) in the cube, to an outputcolorant indicated by a node value. More specifically, each node (309)is indexed by the input color model colorants (e.g., R,G,B as depictedin FIG. 3) and a node value indicates the output colorant combinationthat generates an output colorant corresponding to the input colorantfor that node (309).

In general, a color table may be defined by the number of nodes along aparticular axis. For example, a color table with five nodes along eachaxis may be referred to as a 5-cubed color table. By comparison, a colortable with seventeen nodes along each axis may be referred to as a17-cubed color table. The accuracy of the color transformation dependson the number of nodes of the color table. In some examples, theaccuracy of the color transformation may be referred to as theresolution of the color table. For example, a 5-cubed color tablegenerates a less accurate output representation of the input colormodel. This may also be referred to as a low-resolution color table. Bycomparison, a 17-cubed color table generates a more accurate outputrepresentation of the input color mode. This may be referred to as ahigh-resolution color table.

In some examples, the compressed color table (205) may be a highresolution color table. For example, the compressed color table (205)may consist of seventeen nodes (309) along each axis (306, 307, 308) ofthe cube. In another example, the compressed color table (205) may be amulti-resolution color table. More specifically, a number of nodes (309)may have an intermediate resolution, and a number of other nodes (309)may have a high resolution. For example, differences in vivid colors areless easily perceived by the human eye. Accordingly, nodes (309)corresponding to these vivid colors may have an intermediate resolution.By comparison, differences in “near-neutral” colors (i.e., colors closeto a neutral axis of the cube) are more easily perceived by the humaneye. Accordingly, nodes (309) corresponding to these near-neutral colorsmay have a higher resolution.

The compressed color table (205) may correspond to a particular mediatype. For example, particular paper types, or particular paper colorsmay have corresponding compressed color tables (205). For example, onecompressed color table (205) may correspond to plain paper and anothercompressed color table (205) may correspond to thicker paper, such ascompany letterhead, or bond paper. In another example, different degreesof output quality may have different compressed color tables (205). Forexample, a “draft” quality may have one compressed color table (205),and a “best” quality may have a different compressed color table (205).In yet another example, different input devices (FIG. 1, 101) may havedifferent corresponding compressed color tables (205). For example, amobile device may have one corresponding compressed color table (205),and a digital camera may have a different corresponding compressed colortable (205).

A number of the nodes (309) of the compressed color table (205) maycorrespond to nodes of a seed color table. The seed color table may be alower-resolution, and distinct, version of the compressed color table(205). For example, the compressed color table (205) may be a 17-cubedcolor table and the seed color table may be a 5-cubed color table.

A number of other nodes (309) of the compressed color table (205) may bedelta nodes that correspond to a number of delta tables. An example ofdelta nodes is given as follows. According to an example, a seed colortable may be a low resolution version of the compressed color table(205). For example, the seed color table may be a 5-cubed table. Fromthis seed color table, an intermediate color table (a 9-cubed table, forexample) may be interpolated using linear interpolation, tetrahedralinterpolation, or any other type of interpolation. Interpolation mayinclude generating a number of nodes unique to the intermediate colortable. For example, a number of unique nodes may be interpolated byfurther dividing the planes of the seed color table. Accordingly, theinterpolated intermediate color table may include 1) a number of nodesthat correspond to the seed color table nodes and 2) a number of nodesthat have been interpolated from the seed color table. The number ofnodes that have been interpolated may be unique to the interpolatedintermediate color table.

Regarding the nodes that are unique to the interpolated intermediatecolor table, the interpolated node values may be compared to node valuesof an actual (and not interpolated) intermediate color table, and thedifferences or “deltas” stored in a first delta table. From the firstdelta table and the seed color table, an intermediate “seed/delta” colortable may be generated. As described above, the intermediate“seed/delta” color table may include 1) a number of nodes thatcorrespond to the seed color table nodes and 2) a number of delta nodesthat correspond to the first delta table.

The intermediate “seed/delta” color table may be different from theinterpolated intermediate color table in that the interpolatedintermediate color table includes a number of interpolated nodes whilethe intermediate “seed/delta” color table includes a number of deltanodes. The interpolated nodes including an interpolated node value andthe delta nodes including a corresponding difference from the firstdelta table.

From this intermediate “seed/delta” color table, a final color table (a17-cubed table, for example) may be interpolated using linearinterpolation, tetrahedral interpolation, or any other type ofinterpolation. Interpolation may include generating a number of nodesunique to the final color table. For example, a number of unique nodesmay be interpolated by further dividing the planes of the intermediatecolor table (the 9-cubed color table). As such, the interpolated finalcolor table may include 1) a number of nodes that correspond to the seedcolor table nodes, 2) a number of nodes that correspond to theintermediate seed/delta color table and 3) a number of nodes that havebeen interpolated from the intermediate “seed/delta” color table. Thenumber of nodes that have been interpolated may be unique to theinterpolated final color table.

Regarding the nodes that are unique to the interpolated final colortable, the interpolated final node values may be compared to node valuesof an actual (and not interpolated) final color table, and thedifferences or “deltas” stored in a second delta table. From the firstdelta table, the second delta table, and the seed color table, acompressed color table (205) may be generated. As described above, thecompressed color table (205) may include 1) a number of nodes thatcorrespond to the seed color table nodes, 2) a number of delta nodesthat correspond to the number of delta tables. More specifically, thecompressed color table (205) may include nodes corresponding to 1) theseed color table, 2) the first delta table indicating differencesbetween an interpolated intermediate color table and an actualintermediate color table for those nodes in the intermediate color tableand not the seed color table, and 3) the second delta table indicatingdifferences between an interpolated final color table and an actualfinal color table for those nodes in the final color table and not theintermediate color table.

The compressed color table (205) may be different from the interpolatedfinal color table in that the interpolated final color table includes anumber of interpolated nodes while the compressed color table (205)includes a number of delta nodes. The interpolated nodes including aninterpolated node value and the delta nodes including a valuecorresponding to a delta value from the second delta table.

The compressed color table (205) has a first level of compression byusing the differences from the delta tables instead of actual colorantamounts for a number of nodes (309). The compressed color table (205)may have been further compressed by reducing a number of values in thedelta tables. As described above, delta values may indicate thedifference between an actual node value and an interpolated node value.In some examples, delta values may be reduced. For example, each deltavalue may be judged and potentially reduced based on colorimetry,perception, or a combination thereof. More specifically, each outputcolorant at each node, with its given delta, can be analyzed and a lowerdelta value in the delta table (a delta value closer to, or equal tozero, for example) can be assigned where the color difference isperceptually insignificant. An output colorant value for a node may beassigned that results in a lower delta value. For example, a colorantvalue (or amount) that gives a lower delta value may be greater orsmaller than the default colorant value. In another example, the reducedvalues may be based on memory device (FIG. 2, 204) characteristics. Forexample, least significant deltas (i.e., those pertaining to colors thatare least susceptible to difference detection) may be reduced (to zero,for example), until the compressed color table (205) is a size thatcomplies with the storage capabilities of the memory device (FIG. 2,204).

Reduced delta values in the delta tables of the compressed color table(205) further decreases the size of the compressed color table (205) andallows the compressed color table (205) to be stored on small storagedevices, such as the memory device (FIG. 2, 204) implemented alone, ordisposed on, a printer cartridge (FIG. 1, 103).

A second level of compression is exhibited by the compressed color table(205) by representing a string of zero value entries in the delta tablesas a length. For example, the first delta table and the second deltatable may have significant repeating runs of zero delta entries. Toefficiently represent data that will have many repeating zero entries, amost significant bit may indicate the beginning of a string of zerovalue entries. If that bit is set, the remaining bits define the numberof zero delta entries. Representing a string of zero value entries maybe understood as run length encoding. Representing a string of zerovalue entries with a most significant bit and remaining bits thatindicate the string length may be beneficial in that it creates adistribution of data with low entropy that further compresses thecompressed color table (205).

Another level of compression may be exhibited by the compressed colortable (205) by delta tables that have been ordered in a way to improvecompression. In a color table, the low chromatic input colors are morelikely to generate non-zero entries in a delta table. By comparison,high chromatic input colors are more likely to generate low, or zero,delta table values. Accordingly, a delta table may be ordered from leastchromatic to most chromatic color input. In such a delta table, entriesthat are most likely to be non-zero (the least chromatic colors) aregrouped, and the entries that are most likely to have low or zero deltavalues (the most chromatic colors) are also grouped together. A deltatable as described may have increased strings of zero value entries. Adelta table that is arranged according to chromatic properties of theinput colors may be beneficial in that it increases the size ofzero-value runs and therefore is further compressed and has lower dataentropy. While a delta table ordering based on chromatic colorproperties has been described, many other delta table orderings may beused. The particular delta table ordering may be based on ink propertiesor color table properties.

The reduced size, allows for the compressed color table (205) to bestored on the memory device (204), which as described is beneficial inthat it allows for greater flexibility and customization in adjustingthe color mappings. Additionally, a compressed color table (205) thatcomprises a number of nodes (309) that correspond to nodes of a seedcolor table increases the quality of the compressed color table (205) asthe seed color table is less subject to entropy, thus increasing thecompression amount of the compressed color table (205). It should benoted, that while 5-cubed, 9-cubed and 17-cubed versions of a colortable have been indicated as seed, intermediate and final resolutionvalues, any number and any resolution color table may be implemented asdescribed above.

FIG. 4 is a diagram of a compressed color table (205), according to oneexample of the principles described herein. More specifically, a portionof the compressed color table (205) is depicted in FIG. 4. FIG. 4depicts those nodes (309 a) of the compressed color table (205) thatcorrespond to the seed color table, those nodes (309 b) that correspondto the first delta table, and those nodes (309 c) that correspond to thesecond delta table. As described above, a number of lines (411) maydivide a color table into a number of nodes (309) and a color table maybe defined by the number of nodes (309) along each axis of the colortable. For example, in FIG. 4, a first set of lines (411 a), indicatedas solid lines, may divide each axis of a color table into 5 nodes,resulting in a 5-cubed table. The intersection of two lines (411 a) ofthe first set results in a first set of nodes (309 a) that correspond tothe seed color table. For simplicity, in FIG. 4, just one of the firstset of nodes (309 a) is indicated by a reference numeral; however eachintersection of lines (411 a) of the first set results in a node (309 a)of the first set. As described above, the compressed color table (205)may include a number of nodes (309 a) that correspond to the seed colortable. In the compressed color table (205) the node values for thesenodes (309 a) may be the output colorant amount.

As described above, a lower resolution color table may be used tointerpolate a higher resolution color table. For example, additionallines (411 b), indicated as dashed lines, may further divide each axisof the color table. The intersection of a line (411 b) of the second setwith a line of the first set (411 a) or a line of the second set (411 b)may result in a second set of nodes (309 b) that correspond to nodesbased on the first delta table.

Similarly, additional lines (411 c) indicated as dash-dot lines, may yetfurther divide each axis of the color table. The intersection of a line(411 c) of the third set with any other line (411 a, 411 b, 411 c) mayresult in a third set of nodes (309 c) that correspond to nodes based onthe second delta table. Accordingly, the nodes of the compressed colortable (205) may include nodes (309 a) that correspond to the seed colortable, nodes (309 b) that correspond to the first delta table, and nodes(309 c) that correspond to the second delta table.

FIG. 5 is an example of a compressed color table (205), according to oneexample of the principles described herein. As described above, thecompressed color table (205) may be divided by a number of lines (411)that result in a number of nodes (309) of the compressed color table(205). For simplicity, just a few lines (411) and nodes (309) have beenindicated on FIG. 5 with reference numerals. In some examples, thecompressed color table (205) may be a high-resolution color table. Inother words, the compressed color table (205) may include 17 nodes alongeach axis. It should be noted that while 17 nodes is indicated as highresolution, any number of nodes along an axis may indicate highresolution. For example, 33 nodes may indicate a color table is afull-resolution color table.

The compressed color table (205) also comprises a losslessly compressedneutral axis (510). More specifically, the losslessly compressed neutralaxis (510) may be digitally lossless, which as described above, is acompression process in which no data is lost. Accordingly, thelosslessly compressed neutral axis (510) may be a full-resolutionneutral axis (510). As described above, changes to colors that fallalong the neutral axis (510) are more easily detected by the human eye.Accordingly, it may be desirable to increase the resolution along theneutral axis (510) to increase the accuracy, or overall quality, of thecompressed color table (205). In some examples, one of the origin node(309 d), or the node (309 e) farthest from the origin node (309 d),represents the color black, while the other represents the color white.Including a losslessly compressed, or full resolution, neutral axis(510) is beneficial in that it enhances the accuracy of the colortransformation, as it increases the resolution for those nodes (309)that are most likely to be noticed if they are different.

FIG. 6 is an example of a compressed color table (205), according to oneexample of the principles described herein. As described above, thecompressed color table (205) may include a number of nodes (309 a) thatcorrespond to the seed color table. In FIG. 6, in addition to thosenodes (309 a) indicated, the intersection of two solid lines indicatesnodes that correspond to seed color table nodes.

Additionally, the compressed color table (205) includes nodes (309 b)that correspond to a number of delta tables. In other words, nodes thatdo not exist in the seed color table and do not exist in the losslesslycompressed neutral axis (FIG. 1, 510). In FIG. 6, in addition to thosenodes (309 b) indicated, the intersection of a dashed line with a solidline or another dashed line indicates nodes (309 b) that are based on afirst delta table. In FIG. 6, in addition to those nodes (309 c)indicated, the intersection of a dash-dot line with any other line(solid line, dashed line, or a dash-dot line) indicates nodes (309 c)that are based on a second data table.

The compressed color table (205) may also have been compressed using atraditional compression encoding scheme such as Lempel-Ziv-Welch (lzw)compression, Lempel-Ziv-Markov chain algorithm (lzma) compression, gzip,or other compression techniques.

A compressed data table (205) that comprises a number of nodes (309)that indicate the difference between an interpolated value and an actualvalue (Le., the delta tables) may be beneficial in that the size of thecompressed data table (205) is reduced as just the differences arestored, rather than the actual amount of output colorant. One example ofthe compression rates for the compressed color table (205) is given inTable 1. Table 1 indicates the compression results for an example inkset, for printing on plain paper.

TABLE 1 Original Run Length Compression Size Run length Encoding withCompression Level (bytes) Encoding lzma Compression Ratio 0 (lossless)19652 10201 5207 3.8:1 1 19652 6134 3573 5.5:1 2 19652 4511 2807 7.0:1 319652 3550 2312 8.6:1 4 19652 2911 1965 10.1:1  5 19652 1936 131014.7:1  6 19652 1387 938 19.9:1  7 (no deltas) 19652 700 435 45.2:1 

In Table 1, level 0 is a lossless compression. In other words there isno difference between the reconstructed data and the original data. Atlevel 7, the first delta table and the second delta table are discarded.

The specification and figures describe a printer cartridge (FIG. 1, 103)comprising a memory device (FIG. 2, 204) that contains a number ofcompressed color tables (FIG. 2, 205). The compressed color tables (FIG.2, 205) comprise a losslessly compressed neutral axis (FIG. 5, 510), anumber of nodes (FIG. 3, 309) that correspond to seed color table nodesand a number of delta nodes (FIG. 3, 309) that are based on a number ofdelta tables. The delta tables indicate differences between interpolatedcolor table nodes and corresponding actual color table nodes.

A memory device (FIG. 2, 204) for use in a printer cartridge (FIG. 1,103) is described. The memory device (FIG. 2, 204) contains a number ofcompressed color tables (FIG. 2, 205). The compressed color tables (FIG.2, 205) comprise a losslessly compressed neutral axis (FIG. 5, 510), anumber of nodes (FIG. 3, 309) that correspond to seed color table nodesand a number of delta nodes (FIG. 3, 309) that correspond to a number ofdelta tables. The delta tables indicate differences between interpolatedcolor table nodes and corresponding actual color table nodes.

A compressed color table (FIG. 2, 205) stored on a memory device (FIG.2, 204) that is either programmed to be used with, or disposed on aprinter cartridge (FIG. 1, 103) may have a number of advantages,including: (1) offering improved ink types that didn't exist at the timethe original product was manufactured; (2) correcting color tables inprinters after start of manufacturing of an output device (FIG. 1, 102);(5) correcting color tables for changes in media; and (6) supportingmedia types that didn't exist at the time an output device (FIG. 1, 102)was manufactured. Additionally, a compressed color table (FIG. 2, 205)that comprises a seed color table and a number of delta tables may havea number of advantages, including: (1) introducing output media withdifferent color characteristics without requiring the customer toreplace all supplies to correct for errors; and (2) introducing improvedcolor tables for a single color without requiring the customer toreplace all supplies to correct for errors.

The preceding description has been presented to illustrate and describeexamples of the principles described. This description is not intendedto be exhaustive or to limit these principles to any precise formdisclosed. Many modifications and variations are possible in light ofthe above teaching.

What is claimed is:
 1. A printer cartridge, comprising: a memory device;at least one compressed color table provided by the memory device,comprising: a losslessly compressed neutral axis; a number of nodes thatcorrespond to seed color table nodes; and a number of delta nodes thatcorrespond to a number of delta tables; in which the number of deltatables indicate differences between interpolated color table nodes andcorresponding actual color table nodes; and an ink reservoir to containink, wherein the at least one compressed color table is used duringejection of ink from the ink reservoir.
 2. The printer cartridge ofclaim 1, in which: a first delta table indicates a difference between aninterpolated intermediate color table and an actual intermediate colortable; and a second delta table indicates a difference between aninterpolated final color table and an actual final color table.
 3. Theprinter cartridge of claim 2, in which the first delta table, the seconddelta table, or a combination thereof include a number of reduced deltavalues.
 4. The printer cartridge of claim 3, in which the reduced deltavalues comprise values reduced based on colorimetry, perception, or acombination thereof.
 5. The printer cartridge of claim 2, in which thefirst delta table, the second delta table, or a combination thereof havebeen arranged based on properties of an input color model.
 6. Theprinter cartridge of claim 5, in which the first delta table, the seconddelta table, or a combination thereof have been arranged such that inputcolors with low chromatic properties are grouped together, and inputcolors with high chromatic properties are grouped together.
 7. Theprinter cartridge of claim 2, in which the first delta table, the seconddelta table, or a combination thereof comprise a representation of astring of zero delta values as a length of the string.
 8. The printercartridge of claim 1, in which the compressed color table includes nodesof different resolution.
 9. The printer cartridge of claim 1, in whichthe compressed color table is specific to the printer cartridge.
 10. Theprinter cartridge of claim 1, in which the compressed color tablecorresponds to a particular media type.
 11. The printer cartridge ofclaim 1, in which the compressed color table corresponds to a particularoutput quality.
 12. The printer cartridge of claim 1, in which thenumber of delta nodes comprises a first number of delta nodes thatindicate differences between an interpolated intermediate color tableand an actual intermediate color table.
 13. The printer cartridge ofclaim 12, in which the number of delta nodes comprises a second numberof delta nodes that indicate differences between an interpolated finalcolor table and an actual final color table.